...but I have absolutley no idea where to start, I've been browsing the forum, but can't really find any kind of step by step blueprint. I see a bunch of different threads for like the visor and for the scanner, but nothing about the actual helment mold. Should I just use other people as referances?

I also have no idea what material to use? Sintra?

I'm still new to the site, so it's perfectly possible that I missed some sort of obvious thread that has this info

WOF's templates are great and quite a few people have made them. There's Antman's 2 builds/tutorials, which are very detailed, and one by Honus which is also pretty good. There's also someone doing a WOF helmet with Sintra, I forget who. So you can follow that if you want to use sintra.

The no. 1 rule though: search is your friend. Just search for scratch build. I don't think any of the threads I mentioned are beyond the first 3 pages of the Helmet section, because I'm pretty sure I've seen them fairly recently. Other than that, good luck.